There is increasing interest in microtonal music, but presently there are no instruments designed to accurately and repeatably play a variety of microtonal music. The term microtonal music refers to scales having pitches different from the standard twelve half-tones per octave. Most conventional instruments, including the piano, are designed to generate twelve equal-tempered half-tones per octave, there being seven diatonic tones and five intermediate tones which are represented by accidentals.
Microtonal music typically involves equal-tempered microtonal increments of quarter-tones, sixth-tones, or twelve-tones which generate twenty-four, thirty-six and seventy-two different pitches, respectively, per octave. Microtonal music is presently played on many orchestral and band instruments through alternative fingerings, innovative lip positions, or other techniques specific to the individual instrument. However, a great deal of practice and effort is required to accomplish these techniques, and accurate, repeatable renditions of the microtonal music are difficult at best.
While microtonal music may be finessed on many instruments, it is simply not possible to produce microtonal music on conventional keyboards such as the piano unless the actual tuning of each key is altered. Since a piano has only 88 keys, no more than 88 distinct pitches are possible on that instrument.
One keyboard, described in U.S. Pat. No. 3,012,460 granted to Wilson, carries thirty-one keys per octave to produce thirty-one different tones of equal temperament for each octave. However, this keyboard is still based on the arrangement of a conventional piano. For example, the keys are arranged in five rows, the central row containing seven diatonic tones per octave corresponding to the white keys of the piano, and the row above it containing keys corresponding to the five black keys per octave of a conventional piano. This relationship is constraining for the playing of microtonal music having scales other than thirty one tones per octave.